Ultra high frequency conductor



Jan. 13, 1948. c, OKRESS 2,434,509

ULTRA HIGH FREQUENCY CONDUCTOR Filed June 19, 1943 INVENTOR .E'. 6. 0109555 BY W WWW- ATTORNEY Patented Jan. 13, 1 948 ULTRA HIGH FREQUENCY CONDUCTOR Ernest C. Okress, Montclair, N. 1., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of'Pennsylv-ania Application June 19, 1943, Serial No. 491,453

6 Claims. (01. 178-44) This inventionrelates to ultra high frequency conductors and more particularly to coupling joints or junctions constituting parts thereof, and the specific improvement is exemplified in its utilization in a coaxial line conductor.

Transfer of electrical energy in the form of electromagnetic waves in coaxial lines is an established fact and of constant application both in laboratory and field Work. Essentially the means employed is a hollow conductive pipe having a rod or other conductor therein of considerably smaller diameter and coaxial therewith. The interior surface of the outer tubular conductor-or pipe and the exterior surface of the interior conductor or rod in performing their conductive functions are subjected to transmission longitudinally. The problem of joining sections of such lines has been one of difliculty to overcome. In some instances the joints, when accessible, have been soldered. Another common expedient has been to utilize one type or another of friction joint, but since the line at the joint must pass intense ultra high frequency currents, a friction joint is subject to sparking, corona, corrosion and other detrimental effects. Such a solution therefore has limited efficiency and dependability. The employment of coaxial line conductors remains a necessity in many instances and solution of the problem of satisfactorily joining sections eificiently is of paramount interest.

A copending patent application, Ser. No. 464,824, filed by me November 6, 1942, and assigned to the same assignee as the present case, deals with solution of the problem of joining sections of hollow wave guides. The present invention improves upon the construction disclosed in the prior application and extends my invention to a solution of the problem of coupling sections of coaxial line conductors.

It must be emphasized that common types of friction joints are generally inefiicient when used in lines conveying large microwave energy and that prior practice has been directed largely to obtaining surface continuity by soldering or by using especially designed friction joints. These modes of forming joints are fairly satisfactory for the electrical conductivity requirements, but have their deficiencies from practical considerations. Principal among the shortcomings of the'prior art practice is the difficulty involved in making changes, additions and substitutions in the assembly. The solder-joint method of assembly of the prior art presents even more of a problem in the construction and use of coaxial lines than in hollow wave guides in view of the necessity to make sealed junctions of the inner conductor sections which are inaccessible to the workman due to position thereof within the hollow conductor. Friction joints are equally inaccessible and cannot be inspected after assembly.

The present invention accordingly has for its general object the provision of an improved, effective and efiicient coaxial line joint.

Likewise, from a general aspect, an object of the invention is to provide a cavity and coaxial line joint or coupling which is readily assembled or completed and readily disconnected when desired.

More specifically, an object of the invention is to provide a coaxial line joint which obtains desired electrical continuity with threaded or guided connections obtaining the mechanical continuity.

Another object of the invention is to provide a structure enabling the inner conductor tobe assembled without need of direct access thereto for the purpose.

A further object of the invention is to provide a structure enabling assembly of the inner conductor by manipulation of the outer conductor.

Yet another object of the invention is to reduce to a minimum reflection of the energy due to mismatch at the coupling of the conductors.

Still further objects will appear as the description progresses, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing in which like numerals of reference indicate similar parts throughoutthe several views:

Figure 1 is a vertical-longitudinal section of a coupling in a microwave coaxial line conductor exemplifying one embodiment of the invention;

Figure 2 is a vertical-longitudinal section similar to Fig. 1 and showing that part of the coupling means which is on one section of the coaxial line conductor;

Figure 3 is a similar vertical-longitudinal section showing the complementary coupling portion of the other section alone; and

Figure 4 is a cross section on line IV-IV of Fig. 1.

In the specific embodiment of the invention illustrated in said drawing, the reference numerals I9 and II designate outer alined hollow conductive sections of a coaxial wave guide, preferably cylindrical, and numerals I2 and I3 designate the corresponding inner conductors or rods for each section, said inner conductors likewise being cylindrical and coaxial with the respective sections in which situated. As usual with coaxial line conductors, the inner rod is supported at intervals of its length by suitable means, such as glass beads I4 from the outer conductor or tube so as to maintain the coaxial relationship or by wide band stub supports.

Generally speaking, the hollow outer sections of the coaxial line have their ends substantially abutting and mechanically coupled together in a manner very similar to the coupling of the wave guide sections as described in said copending application Ser. No. 464,824. Such mechanical coupling is accomplished by employment of complementary girdling members I5, I6, one on the marginal end portion of one section ii) and the other on the marginal end portion of the other section II and each secured, as by soldering, to its respective section. These girdling members I5, I8 are of course electrically conductive, and in practice are made of brass or other suitable metal. Since the outer conductor sections I8, II are cylindrical, the said complementary or girdling members are of ring formation. One of said members, as I5, provides a peripheral flange I? and the other member II is peripherally threaded, enabling a clamping ring I8 to be applied over and have bearing behind the flange, said clamping ring being internally threaded to screw upon the threaded periphery of member I6, completing the assembly. Preferably the ends of the hollow outer conductors are of equal size and shape and in proximity to each other, but leave a gap 19 of small dimension therebetween.

In order to accomplish a rigid clamping of the complementary members and at the same time maintain the small gap IS between the facing ends of the hollow conductor sections, a forwardly projecting cylindrical rib 2c is provided from the forward face of one member, as-I5, to engage at its forward edge with the complementary member I8. This rib 2B is also constituted as a means for coaxially alining the sections and members, for which purpose the rib is made coaxial with the section and the complementary member is provided with a coaxially disposed groove 2I in its forward face and of appropriate diameter and size to receive the rib. It is engagement of the end of the rib with the bottom of the groove which determines gap I9 for the spacing of the ends of the sections. Said rib and groove also function to situate the contiguous ends of the sections.

The complementary member I having rib 2G is also provided with an annular recess or slot 22 extending from said gap I9 approximately a half wave-length (referring to the wave-length of the particular coaxial line) and so proportioned for purposes hereinafter set forth. Said recess preferably is constructed to double back upon itself so as to obtain the desired half wave-length depth without undesirably increasing the length of the coupling member. This feature is accomplished by forming member I5 of coaxial rings, of which the outer one 23 provides the aforementioned flange I1 and rib 20 at its forward end, and provides an inwardly directed boss 24 at its rearward end to fit over the peripheral end margin of inner ring 25 which in turn has a similar boss 26 fitting over the conductor section Ill at the end margin thereof. The inner ring 25 overlaps complementary conductor section II thereby forming part of the annular recess 22 between said ring and conductor and forming a right-angle continuation of gap I9. The forward end of inner ring 25 stops short of complementary member I8, and since it is spaced from outer ring 23 as far as boss 24, recess 22 continues around the end of said inner ring and along the outside thereof, terminating at said boss 24. The two rings 23, 25 are soldered at their ends having bosses 24 and 26 thereby constituting them effectually integral and electrically continuous.

In use, the structure described obtains a virtual electrical continuity for microwave currents, notwithstanding small physical spacing or presence of gap I9, at the contiguous or adjoining ends of the outer conductor, the theory of which is explained in said copending application. Said recess, having the doubled-back configuration above described, constitutes a half wave shorted section open at its forward end at gap I9 and having its rearward end closed by boss 24 where it reflects a low impedance which is transformed to a correspondingly very low impedance across the gap at entry thereof into the outer conductor around the periphery thereof at gap I8. This gap impedance is negligible, as a result of which the gap is electrically eliminated to radio frequency and the wave energy in the conductor passes the junction of the sections with a minimum of reflection and hence with high efliciency of transfer so far as influence of the outer conductor thereon is concerned.

The inner coaxial conductor or rod in the embodiment shown is separable at substantially the same place of junction as the outer conductor, one section I2 of the rod being shown with a forwardly facing shoulder 21 in the plane of the forward end face of the corresponding outer conductor and radially inward from gap I9. Projecting longitudinally forwardly from and coaxial with the shoulder 21 is a collar 28 of less diameter than the rod conductor, and within this collar coaxial therewith is a stem 29. The stem is longer than the collar and projects forwardly beyond the same and is there shouldered radially inward at 30 and projects forward with reduced diameter from the stem to provide a tip 3 I, shown in this instance as threaded as illustrative of one means of attachment to the next section.

A sleeve 32 having an outer diameter equal to that of the rod conductor is situated coaxially around the collar 28, said sleeve having a forward end margin fitting over and rigidly held by a reduced end margin of the rod-conductor section I3. A solder joint 33 is made between said sleeve and the rod conductor so the sleeve is virtually a part of the conductor. The other end of said sleeve constituting the virtual end of conductor I3 stops short of the shoulder 21 on the other rod conductor section I2, thereby affording a gap opening I9 between those parts. Tip 3I may be releasably secured in a prepared socket in the end of conductor I3, both being here shown as threaded as one example of releasable attachment, whereas the other end of said stem is permanently soldered or otherwise made integral with the other conductor rod section I2. The inner diameter of the sleeve is somewhat greater than the collar and the collar is somewhat greater in inner diameter than thestem, thereby providing a doubled-back annular cavity or slot 3d therebetween with the end wall of conductor l2 at thepart thereof between the stem and collar constituting a closed end for said cavity or slot and gap l9 forming an open end therefor. With the parts thus assembled, sleeve 32 is virtually apart of the rod section i3 to which it is sol-- dere-d, and the gap-forming end of the sleeve is alined with the adjoining rod section i2 so that their end peripheries are contiguous and separated by gap 19.

Length or depth of said doubled-back slot or cavity 34 is substantially equal in length to a half wave-length (referring as before to the particular wave-length of the coaxial line) from gap l9 to the closed end within the collar 28. In accordance with previously expounded theory, the structure described obtains a virtual electrical continuity for R, F. currents, notwithstanding physical spacing or presence of gap l9, at the contiguous peripheral end edges of the inner conductors at opposite sides of gap. The end wall of the conductor within the collar forming the closed end of the slot or cavity reflects a low impedance along the cavity to a correspondingly very low impedance across the gap I9 at entry thereof between the periphery of shoulder 2'! and contiguous end of sleeve 32 which in effect is part of rod section I3. The impedance at the gap periphery is almost zero as a result of which the gap is electrically eliminated to radio frequency and the wave energy in the conductor passes the junction of the rod sections with a minimum of reflection and hence with high efiiciency of transfer. For wider frequency band, it is within the scope of the invention to duplicate the half -wave impedance cavity, here shown on one end of one section by a similar halfwave impedance cavity in the opposing end of the adjoining section which would thereby obtain a full wave-length path in the cavities juxtaposed to a common gap, both with respect to the inner conductor and outer conductor.

It may now be noted that the construction is one which affords a rigid attachment of the outer conductor sections together and a rigid attachment of the inner or rod conductor sections togeth-er, which is a complete connection of very efiicient electrical and mechanically rugged character and one wherein impedance due to the connection or joint is very low. Since high impedance occurs at the threaded surface contacting parts of the assembly, the contacts made by those parts are effective and are not subject to sparking or other breakdown effects. The gaps betwee contiguous ends of the conductors are made as small as practicable for reducing the voltage drop.

While the foregoing description has been directed to one specific embodiment of the invention, other mechanical constructions may be employed in the actual use thereof.

I claim:

1. An ultra high frequency conductor coupling comprising a pair of alined conductor sections, a stem interposed between end parts of said conductors, one of said conductors having a collar girdling said stem and spaced radially outward therefrom for providing a cavity within said section around said stem, and said stem projecting beyond the said collar and spacing the end of said collar from the opposed end of the other section.

2. An ultra high frequency conductor coupling comprising a pair of alined conductor sections, a stem interposed between end parts of said conductors, one of said conductors having a collar girdling said stem and spaced radially outward therefrom for providing a cavity Within said section around said stem, and said stem having a threaded tip at one end thereof threaded into the adjoining end of the opposed section.

3. An ultra high frequency conductor coupling.

section comprising alined rod sections and of which one rod section has an end portion, a stem projecting axially at said end portion, a collar projecting from said end portion and providing inner and outer cylindrical areas the diameters of which are intermediate of the diameters of the rod section and stem, a sleeve on the other rod section and coaxial with and spaced from said collar, the outer diameter of said sleeve being the same as that of the rod sections whereby the peripheral surface of the sleeve is a continuation of the peripheral surface of said rod sections, and said sleeve and collar each leaving a gap at the end thereof between the same and the respective opposed ends of the rod sections.

4. An ultra high frequency conductor coupling section comprising a rod having a recessed end thereby constituting the end portion of said rod an integral collar with the rod, said rod also providing a smaller socket at the inner end of the recess, a stem secured in said socket and projecting longitudinally of said recess thereby forming an annular cavity around the stem within the collar, said stem projecting from the recess and having an outwardly facing shoulder beyond the end of said sleeve for limiting approach of an adjoining section.

5. A coaxial line coupling means comprising an outer conductor having alined sections providing a gap at the joint between the ends of said sections at a plane transverse to said line, and an inner coaxial conductor having alined sections providing a gap between the ends thereof at the joint between said sections of the inner conductor at a second plane parallel to the first said plane and substantially a quarter wave length distance from the first said plane, means at the meeting pairs of sections for each conductor comprising a wall formation substantially between said planes and each providing a slot opening at a different one of said planes from the other and providing each a closed end at the other plane from the slot, each said slot opening into the gap at the plane next to which the slot has its closed end, for establishing high frequency electrical continuity across the gap at the joint between the sections, means for securing the inner sections together and means for thereafter securing the outer sections together.

6. A coaxial line coupling means comprising an outer conductor having alined sections and an inner coaxial conductor having alined sections, the inner section within an outer section being supported thereby and immovable with respect thereto whereby rotation of the inner conductor section may be effected by rotating the outer conductor section, said inner sections having threaded engagement for securing the same together and the outer conductor having means for securing the sections together subsequent to complete assembly of the inner conductor, and a half-wave shorted line opening between the meeting pairs of sections for each conductor establishing low impedance thereat and effect of 7 direct electrical high frequency continuity across the joints between sections of said pairs of sections.

ERNEST C. OKRESS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Usselman Sept. 16, 1941 Hayford Dec. 15, 1942 Streib Oct. 13, 1942 Roosenstein Feb, 24, 1942 Cork et a1 Apr. 2, 1940 Number Number 

